what is meant by a "runaway" propeller?

[Bomberboy]

One solution was to equip the aircraft with an auxiliary stand-pipe to contain enough reserve oil to feather the prop of a damaged engine that had lost its internal oil.

I'm not sure I've quite understood how you have explained this so please bear with me?
In a standard configured B-17, there is only one oil storage area for each engine and that is the oil tank. The only "engine internal oil" as you have described it, is the oil which happens to be passing through an engine at any given time before collecting into the small sump for scavenging back to the oil tank.
The tank has two pickoff pipes connected to it, one is a reserve 'lower' level pickoff point of oil that remains at the bottom of the oil tank with a separate oil pickoff point and feeder pipe.
The 'normal' running oil level is is fed from a higher pickoff point within the same oil tank right next to the feathering pickoff point. This is via a slightly extended pipe into the tank. This maybe what you had in mind with your explanation, but it was not clear to me.
I HTH

[k5083]

Thank you for all the great info guys.

Another question. If airflow is pushing the prop around, could it cause the engine to keep running even with everything turned off, like dieseling or run-on in a car engine?

August

[bdk]

Run on like you get in a car occurs because you turn off the ignition to stop a car engine. If you have hot carbon in the cylinder, it may act like a spark plug and ignite the mixture. The carburetor continues to deliver fuel when the engine is turning. On an aircraft, you typically shut down the engine by putting the mixture control into "idle cutoff," which starves the engine for fuel. Without fuel it can't run nregardless of the spark situation. You then switch off the magnetos after the engine stops. One of the purposes of waiting for the engine to stop is to ensure that all the fuel is out of the engine in case you forget to turn off the switch. With fuel still in the engine you could get an inadvertant start if someone moved the prop. On a modern electronically fuel injected car I suspect that turning off the ignition switch may disable the fuel at the same time.

Some light aircraft engines however do not have an idle cutoff, only a leaning function. Those could certainly run-on. You would then have to turn the fuel valve off (or wait for it to run out of fuel!).

[maxum96]

On a modern electronically fuel injected car I suspect that turning off the ignition switch may disable the fuel at the same time.

That is correct. Turning the ignition off on a car with electronic fuel injection kills the power to the ignition, electronic fuel injectors and fuel pump as well as the computer that manages the engine . You shut a diesel engine off the same way as an aircraft engine, you cut the fuel off.

[Ken]

A windmill start (high speed taxi on the runway to pinwheel an engine whose starter has failed) in a C-130 is done by presetting the blades to an angle known to be conducive to starting rotation. Incidentally, a similar maneuver is done called a buddy start: another airplane positions itself in front and uses its prop blast to spin the offending engine while both airplnes are stationary.

Photo on page 3 of this marathon thread ... viewtopic.php?f=3&t=46088

Ken

[daviemax]

One solution was to equip the aircraft with an auxiliary stand-pipe to contain enough reserve oil to feather the prop of a damaged engine that had lost its internal oil.

I'm not sure I've quite understood how you have explained this so please bear with me?
In a standard configured B-17, there is only one oil storage area for each engine and that is the oil tank. The only "engine internal oil" as you have described it, is the oil which happens to be passing through an engine at any given time before collecting into the small sump for scavenging back to the oil tank.
The tank has two pickoff pipes connected to it, one is a reserve 'lower' level pickoff point of oil that remains at the bottom of the oil tank with a separate oil pickoff point and feeder pipe.
The 'normal' running oil level is is fed from a higher pickoff point within the same oil tank right next to the feathering pickoff point. This is via a slightly extended pipe into the tank. This maybe what you had in mind with your explanation, but it was not clear to me.
I HTH

Thanks. The term "standpipe" came from, as I recall, Freeman's Mighty Eighth and I quoted that from memory. Looks like more research is needed to fully clarify the design alteration.

[Larry Kraus]

Here's a good depiction of the oil tank on an early DC-6 that shows the standpipe (item 13).The crosshatched oil below the top of the standpipe can only be accessed by running the feather pump.



Here are pages from a flight manual for a Navy R7V-1 (Connie) concerning the Runaway Propeller Emergency Procedure.









As with Stoney,I had a runaway in a DC-7 just after take-off and used basically the procedure from the manual (the R7V procedure is the same as the DC-7 procedure).It think that it got to 3400 rpm and fortunately feathered okay (the normal take-off RPM is 2900).That said,the engine was frozen up after landing and the oil screens were full of metal.It ended up as a nosecase failure,but I don't know if that was the cause or the effect.I definitely don't want another runaway prop.Mine was #4 engine and I didn't hear any unusual noise from the prop,but things happen very rapidly.Fortunately,Dave Kelly (our Chief Pilot) was in the engineer seat and he pointed to the #4 tach,throttled back,tried bumping back the RPM with the toggle switch and immediately hit the feather button when the toggle switch had no effect.I reduced speed by pulling back on the yoke.We had a load of water on board for a practice drop and jettisoned that in a convenient field and landed without further theatrics.

[Bomberboy]

Here's a good depiction of the oil tank on an early DC-6 that shows the standpipe (item 13).The crosshatched oil below the top of the standpipe can only be accessed by running the feather pump.

Larry, I would say that there is a good similarity between this diagram and the B-17 tank fit.
The main difference seems that the feathering pick off point on the diagram shows it in an entirely different place to the B-17 which has both main oil and feathering oil pick off points directly next to each other into the fitting at the bottom of the tank into what the diagram calls a hopper.

Here are pages from a flight manual for a Navy R7V-1 (Connie) concerning the Runaway Propeller Emergency Procedure.

The wording interests me in these manual notes.
It writes about propeller RPM for example as 2900, but my understanding is that the RPM is in fact for the engine and not the propeller as the tachometer giving the RPM indication, is driven by the engine with the propeller turning at many, many less revolutions by comparison.
I can't say what it would be in the this case as I do not know the ratio of the reduction gear fitted to this particular aeroplanes' engines.

[Larry Kraus]

The tachometer reads engine RPM.The prop RPM on take-off with the DC-7 with a 16:9 reduction ratio is around 1631 RPM.

[Ken]

Larry, thanks for taking the time to post those excerpts - very cool.

Incidentally, in another recent thread, I talked about the book "Adak" I just finished reading about a P-3 which suffered a severe overspeed. They reported that the noise and vibration were extreme. I seem to recall the C-130 sim instructors turning on the noise/vibration "realism" only briefly and then turining it off so we could go the the procedures and still communicate. That made an impression.

IIRC, for those interested, the C-130 E/H turns at 1,021 RPM, 13.54 gearbox, engine turns 13,820 at 100% RPM. Overspeed mechanisms kick in at 102.5%, assuming my memory is correct.

Ken